Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $63.86   8.434%   $69.246   $69.25   $69.25   $69.20  
  Purchase #2 $109.98   6.667%   $117.3124   $117.31   $117.30   $117.30  
  Purchase #3 $198.86   8.522%   $215.8068   $215.81   $215.80   $215.80  
  Purchase #4 $237.44   8.270%   $257.0763   $257.08   $257.10   $257.10  
  Purchase #5 $38.29   11.619%   $42.7389   $42.74   $42.75   $42.70  
  Purchase #6 $63.87   5.365%   $67.2966   $67.30   $67.30   $67.30  
  Purchase #7 $215.30   9.631%   $236.0355   $236.04   $236.05   $236.00  
  7 purchase totals = $927.60       $1,005.5125   $1,005.53   $1,005.55   $1,005.40